Period indicator

ABSTRACT

A period indicator including a liquid-permeable substrate and an indicative section which is overlaid on a portion of the substrate and which is formed from a liquid-permeable material having a low light refractive index, the indicator containing a volatile liquid, wherein the indicative section is formed by coating a surface of the substrate with an indicative-section-forming material prepared by mixing a binder and finely divided particulate matter having a low light refractive index, the indicative section is composed of two or more regions, and the regions differ in height from one another as measured from the surface of the substrate, as the coating amounts per unit area of the indicative section forming material in respective regions differ from one another. Since the period indicator can indicate the chemical-containing state stepwise, it is useful for indicating the available period of use of a chemical such as a mothproofing agent, an insecticide, a deodorant, or a fragrance.

TECHNICAL FIELD

The present invention relates to a period indicator with which users candetermine the effective period; i.e., the time remaining untilexpiration, of a liquid chemical or a similar substance. Moreparticularly, the invention relates to a period indicator capable ofshowing the quantity of the remaining liquid, such as a liquid chemical,in a stepwise manner until the liquid arrives at the endpoint of itseffective period.

BACKGROUND ART

Hitherto, in order to warn users of mothproofing agents, insecticides,deodorants, fragrance, and similar products that the term of efficacy ofsuch chemicals is about to expire, there have been proposed varioustypes of period indicators which display the quantity-related status ofthe liquid chemical.

For example, Japanese Patent Publication (kokoku) No. SHO 63-24961 orJapanese Utility Model Publication (kokoku) No. HEI 5-938 discloses asheet structure having an indicative section and impregnated with aliquid chemical. The sheet structure includes a substrate formed of achemical-liquid-permeable material, and, on the entirety or on a portionof one surface of the substrate, the indicative section formed from achemical-liquid-permeable material having a low light refractive index.According to the disclosures of these publications, thechemical-liquid-permeable material having a low light refractive indexfor forming the indicative section employs, for example, amorphoussilica. During the period in which the chemical is present, theindicative section remains transparent, whereas when the chemical hasvolatilized and been lost, the indicative section becomes opaque,whereby the user can know the final stage that the period of efficacy ofthe chemical has expired.

In recent years, there has arisen consumers' need for diversified modesof display, and to meet such need, there have been proposed indicatorswhich can indicate not only the endpoint of the effective period butalso the early stage or mid stage of the effective period.

Japanese Patent No. 3045651 discloses a period indicator havingindicative portions on the surface of a substrate, wherein oneindicative portion can show the final stage of the effective period andadditionally another indicative portion can show an early stage or midstage of the effective period. For showing that the final stage isapproaching, an indicative layer having a low light refractive index isemployed, whereas for showing that the product is in the early stage ormiddle stage of its service life, an indicative layer having a higherreflectance as compared with that of the substrate is employed. Withthis structure, since the display for showing the early stage or middlestage of use persists even when the final stage of service life, wherethe chemical is volatilized and lost, is approaching, measures must betaken so as mask the persisting sign with the sign showing the endpointof the period, or alternatively, the persisting signs are left to showthemselves but together with the sign showing the endpoint of theperiod. In either case, limitations are imposed on the letters or marksto be used for display.

Japanese Patent Application Laid-Open (kokai) No. HEI 8-106251 disclosesuse of a non-woven fabric as the chemical-liquid-permeable indicativematerial having a low light refractive index. It discloses that throughuse of a non-woven fabric whose density is partially changed, betweenthe low density portion and the high density portion, change of colorcan be made to occur with a time lag, thereby permitting display of thelevel of volatilization of the chemical in a stepwise manner. Since thisapproach employs non-woven fabric, separate means such as printing ontothe non-woven fabric is needed so as to display letters or marks.

As many functions for attaining diversified modes of display have beenadded, there have arisen needs for modification of the composition ofthe material that forms the indicative section, making production stepsintricate and increasing costs.

DISCLOSURE OF THE INVENTION

The present invention contemplates to provide a period indicator whichmeets the above-mentioned trend calling for diversified display modes,and specifically, the invention provides a period indicator including anindicative section which is formed from a single component material soas to be able to attain a stepwise display through a simple process,thereby leading to an improved display performance.

The present invention has been accomplished on the basis of thefollowing inventors' finding. When a liquid is contained in a liquidpermeable indicative substrate on which a liquid permeable indicativesection having a low light refractive index is partially overlaid, theindicative section is rendered transparent and thus invisible. Afterthat, when the liquid is allowed to volatilize to thereby reduce theamount of the remaining liquid, indicative signs can be observed moreeasily in portions bearing larger amounts of coating per unit area ofthe indicative section and thus presenting a higher elevation from thesurface of the substrate, as a result of accelerated speed of becomingopaque.

Accordingly, the present invention is directed to a period indicatorcomprising a liquid-permeable substrate and an indicative section whichis overlaid on a portion of the substrate and which is formed from aliquid-permeable material having a low light refractive index, theindicator containing a volatile liquid, characterized in that theindicative section is formed by coating a surface of the substrate withan indicative-section-forming material prepared by mixing a binder andfinely divided particulate matter having a low light refractive index,the indicative section comprises two or more regions, and the regionsdiffer in height from one another as measured from the surface of thesubstrate, as_coating amounts per unit area of the indicative sectionforming material in the two or more regions differ from one another.

The present invention is also directed to a period indicator asdescribed above, in which the two or more regions that form theindicative section are discretely disposed on the substrate.

The present invention is also directed to a period indicator asdescribed above, in which each of the coating amounts per unit area ofthe indicative section forming material in the two or more regions thatform the indicative section is within the range of 4 to 150 g/m², withthe coating amount in a region where the coating amount is the smallestbeing 4 to 40 g/m² and difference in the coating amounts between the twoor more regions being not less than 5 g/m².

In the present invention, no particular limitations are imposed on theliquid-permeable substrate, so long as it meets the followingconditions: has liquid-retaining ability, falls under the class ofso-called porous structured materials, including paper materials (suchas cardboard, filter paper, and synthetic-fiber-admixed paper),non-woven fabric, felt-like fabric, inorganic fiber sheets, and ceramic-or plastic-base porous materials; is capable of transferring in anorderly manner the remaining liquid contained therein in accordance withthe volatilization state of the liquid, and is chemically inert to theliquid to be contained therein. In order to make the sign more clearlyvisible, preferably, the entirety of the substrate or the substratesurface on which the indicative section is formed is colored. So long asthe purposes of the present invention are attained in relation toretention, volatilization, and transfer of liquid, the “substrate” ofthe present invention encompasses the case where a colored layer isprovided on the surface of the substrate.

No particular limitation is imposed on the shape of the substrate, andexamples thereof include sheet, block, and cylinder. Likewise, noparticular limitation is imposed on the geometry of the surface, andeither a flat plane or a curved plane can be employed so long as theindicative section can be formed thereon. To facilitate formation of theindicative section, the substrate preferably has a sheet form, in viewthat this form is advantageous in handling during printing or coating.

In the present invention, the liquid-permeable, finely dividedparticulate matter contained in the indicative-section-forming materialhas low light refractive index. Specifically, it is finely dividedparticulate matter of a white inorganic pigment such as amorphoussilica, kaolin, or calcium carbonate, or an organic pigment such as aplastic pigment. Of these, amorphous silica is preferred. Amorphoussilica may be in the form of any of synthesized amorphous silica finepowder, hydrated amorphous silicon dioxide, and ultra-fine hydratedsilicate powder, and is commercially available under the trade names ofTokusil GU-NP (product of Tokuyama Corporation), Nipgel AZ-200 (productof Nippon Silica Industry Co., Ltd.), and Mizukasil P-78A (product ofMizusawa Industrial Chemicals Ltd.).

The indicative section of the present invention is formed using amaterial prepared by mixing a binder and the above-mentionedliquid-permeable, finely divided particulate matter having a low lightrefractive index. A coloring agent may be incorporated to the indicativesection. In such a case, however, in order to prevent the indicativesection from becoming recognizable when the indicative section containsa liquid and becomes transparent, the color must be a color similar to,or a color that cannot be distinguished from, the color assumed by thesubstrate surface, as determined visually.

Examples of the binder include vinyl acetate, EVA, NBR, SBR, acryliclatex, and other types of latex. Acrylic binders include NikasolRX-301C, Nikasol RX-864S, and Nikasol FX-329 (products of Nippon CarbideIndustries Co., Inc.).

The amount of a binder to be incorporated must fall within a certainrange, wherein below the lower limit the finely divided particulatematter will no longer be held securely, and above the upper limiteffective liquid permeability will no longer be obtained. In the casewhere the indicative-section-forming material is applied by way ofcoating, generally, a preferred amount of the binder falls within arange of 10-30 parts by mass with respect to 100 parts by mass of thefinely divided particle matter. When coating is performed throughprinting, particularly in the case of screen printing, the amount of thebinder is preferably 50 parts by mass or thereabouts with respect to 100parts by mass of the finely divided particulate matter. A polymersubstance, which serves as a viscosity modifier, may also beincorporated.

The indicative section disposed on the surface of the substrate throughcoating forms a layer in which fine particles of a pigment and binderparticles having a smaller size cohere together so as to leave poresbetween the particles. Since the fine particles of the pigment andliquid have a similar refractive index, when the pores in the indicativesection are filled with the liquid, the indicative section becomestransparent. As volatilization of the liquid proceeds, supply of theliquid from the substrate to the indicative section decreases, tothereby leave pores in the indicative section. This results in an opaqueindicative section, which can be visually perceived. Therefore, thethus-configured indicative section can serve as an indicator for theendpoint, which warns that the liquid has been volatilized and theservice term (effective period) has expired.

When the amount of coating per unit area is increased, the height of theindicative section as measured from the substrate surface becomes high.The present inventors have found that development of a sign occursquicker with increasing amount of coating applied per unit area ofindicative section and with increasing height of the indicative sectionas measured from the substrate surface. That is, in the case where twoindicators have substrates of the same size, and are identical in termsof the position of the indicative section disposed on the substrate andthe shape of the indicative section, a difference in the coating amountper unit area of the indicative section—i.e., a difference in the heightas measured from the substrate surface—results in development of a signwith a time lag. Specifically, the greater the height from the substratesurface, the earlier the moment of development of a sign.

One feature of the present invention resides in that the indicativesection is formed of two or more regions, the regions differing in thecoating amount per unit area, and therefore also differing in the heightas measured from the substrate surface. These two or more regionsdevelop signs with a time lag, providing stepwise indication withrespect to the quantity of residual liquid. That is, as volatilizationof the liquid contained in the indicative section proceeds, a regionbearing a larger amount of coating per unit area and thus having agreater height as measured from the substrate surface is subject toinsufficient transfer of liquid, permitting an indication conveyedthereby to become noticeable earlier. Of a plurality of regions, theregion that bears the least amount of coating per unit area and thus hasthe smallest height as measured from the substrate surface comes last todevelop an indication.

In each region of the indicative section, the amount of coating per unitarea is 4 to 150 g/m². An amount less than 4 g/m² is not preferredbecause low masking performance and insufficient indicative function mayresult, whereas if the amount of coating is increased, repetition ofprinting or a similar coating operation may be required, permitting easyoccurrence of failure such as printing mackle. Therefore, the upperlimit of the coating amount per unit area is preferably 150 g/m². Amonga plurality of regions, the region bearing the least amount of coatingpreferably has a coating amount of 4 to 40 g/m², more preferably 10 to40 g/m².

The difference in coating amount between different regions is preferablynot less than 5 g/m², more preferably not less than 10 g/m², still morepreferably not less than 15 g/m². When the difference in coating amountis less than 5 g/m², respective signs are developed with an unacceptablyshort time lag, resulting in an unclear display.

The height of respective regions that constitute the indicative sectionas measured from the substrate surface is calculated from the density ofthe indicative-section-forming material and the coating amount.Specifically, the height of a region as measured from the substratesurface is obtained through dividing the amount of coating per unit area(g/m²) by the density (g/cm³).

The density of an indicative-section-forming material which is suitablefor forming the indicative section of the present invention ranges from0.3 to 1.2 g/cm³. When amorphous silica is employed as the finelydivided particulate matter, the density falls within a range of 0.3 to0.6 g/cm³. For example, when the density of theindicative-section-forming material is 0.46 g/cm³, a preferred value ofdifference in height between regions differing in terms of coatingamount is 10.9 μm or more.

Even when respective indicative regions have the same coating amount perunit area, if the regions have different sizes, the moment at which asign is developed is affected; i.e., in the case of a larger coated areaand a wider coated portion, sign development tends to occur from theperiphery of the coated portion. Therefore, combination of “differencein coating amount per unit area” and “difference in the area of coatedportion” can attain more clear stepwise indication. That is, theinterval between points in time involved in the stepwise indication canbe prolonged by allotting a larger coating amount and a larger coatingarea to the region intended to develop a sign earlier, and at the sametime, allotting a smaller coating amount and a narrow region width tothe region intended to develop a sign later.

During volatilization of the liquid contained in the indicative sectionof the period indicator of the present invention, the indicative sectionremains transparent and provides no indication. This is because theliquid is sufficiently supplied from the substrate to the indicativesection and thus the pores present in the indicative section are filledwith the liquid. However, when the amount of the transferring liquidbecomes insufficient and the pores present in the indicative section areemptied, the transparency of the section is lost because of diffusion oflight, thereby providing a perceivable indication. Accordingly, in orderto attain a satisfactory stepwise indication, it is preferred that thecoating amount and the coating area of each of the indicative regionsare appropriately adjusted in accordance with its corresponding step ofthe stepwise indication, in consideration of the size, thickness, andliquid content of the substrate. In the case where all the regions ofthe disposed indicative section are relatively small to thereby allowliquid to be sufficiently supplied from the substrate to the regions,there can be obtained a period indicator which provides a stepwiseindication in a considerably late stage of the predetermined period.Also, in the case where a period indicator has large indicative regionsand the substrate is relatively small as compared with the size of theindicative regions, liquid supply to the regions tends to diminish,resulting in a tendency to develop indication from a relatively earlystage of the predetermined period.

Preferably, the indicative section of the period indicator of thepresent invention include regions bearing thereon a coating in differentamounts so as to attain stepwise indication in two to five steps. When aplurality of regions are provided so as to enable an indication mode ofthree or more steps, the indicative effect is further promoted.

Respective regions of the indicative section may be formed to representletters, numerals, symbols, graphics, or combinations thereof.Alternatively, the regions may be configured such that when a coatedportion becomes opaque, the remaining portion (i.e., the uncoatedportion) presents letters, numerals, symbols, or graphics. The regionsare preferably disposed discretely with spaces between the regions.Alternatively, the regions may be disposed so as to abut one anotherwithout any space between the regions. Moreover, in each step ofstepwise indication, the number of regions that develop an indication isnot limited to only one, and a plurality of regions may simultaneouslydevelop such indication.

Also, the indicative section of the period indicator of the presentinvention is designed such that, in accordance with the decrease inamount of the remaining liquid, an indication emerges sequentially fromthe region having the largest amount of coating, and when the regionhaving the smallest amount of coating has come to present an indication,the indicative section as a whole completes its showing of indication.In other words, the indicative section can be designed such that therespective regions sequentially develop signs starting from the regionof the earliest indication, and when the region of the slowestindication has developed its indication, the entire indicative sectionconveys a certain message. This mode is beneficial in that the user ofthe period indicator can received better warning.

All the regions of the indicative section of the period indicator of thepresent invention can be formed by use of a single coating solution.Only repeating a simple process of printing or coating can provideregions of highly indicative effect.

In order to form the respective regions of the indicative section, anyof a variety of coating methods may be employed. Preferably, printing,inter alia, screen printing is employed, and in this case, multi-layerprinting may be performed so as to attain the predetermined amount ofcoating. Also, the indicative substrate having an indicative sectionthereon encompasses, among others, a structure in which a plate-like orfilm-like liquid-impermeable covering made of, for example, a syntheticmaterial (such as polyester or polypropylene) or glass is laminated onone surface of a sheet-like material having, on its opposite surface, anindicative section. In this case, the covering may optionally have alayer of adhesives or sticking agent on a surface thereof. Analogously,the indicative substrate also encompasses a structure in whichindicative sections are disposed on both front and rear surfaces of thesubstrate.

No particular limitations are imposed on the shape and the size of theabove-described indicative substrate, and these factors can bearbitrarily determined in accordance with the purpose of using theperiod indicator. For example, the indicative substrate may have a stripshape of 20 mm×54 mm×400 μm (thickness).

In accordance with the length of the active period of indication andpurpose of use, the liquid to be contained in the indicative substratemay be appropriately selected from among liquids which exhibitvolatility at room temperature or under heat, permeate the indicativesubstrate, and are chemically inert.

When a chemical which effectively exhibits mothproofing effect,insecticidal effect, or a similar effect is used as the liquidexhibiting volatility, the resultant period indicator serves as anindicator showing the period of efficacy of such a chemical per se.

In the case where a liquid exhibiting no chemical effect is employed,the species and the volume of the liquid are determined so as to fit theeffective period of a chemical that requires indication of period.

Some examples of chemicals which exhibit volatility at room temperatureor under heat and which can be employed in the period indicator of thepresent invention are listed below. Those chemicals which exhibitvolatility under heat; i.e., which are solid at room temperature and canbe used when liquefied after heated to a temperature above the meltingpoint are accompanied by their melting point data.

Examples of mothproofing agents and insecticides includeO-(2,2-dichlorovinyl)-O,O-dimethyl phosphate,1-ethynyl-2-methyl-2-pentenyl3-(2-methyl-1-propenyl)-2,2-dimethylcyclopropanecarboxylate,2-methyl-3-allyl-4-oxo-2-cyclopenten-1-yl2,2,3,3-tetramethylcyclopropanecarboxylate,2,3,5,6-tetrafluoro-4-methoxymethylbenzyl3-(1-propenyl)-2,2-dimethylcyclopropanecarboxylate,2,3,5,6-tetrafluoro-4-methylbenzyl3-(1-propenyl)-2,2-dimethylcyclopropanecarboxylate,2,3,5,6-tetrafluoro-4-methoxymethylbenzyl3-(2-methyl-1-propenyl)-2,2-dimethylcyclopropanecarboxylate,2-methyl-3-allyl-4-oxo-2-cyclopenten-1-yl3-(2-methyl-1-propenyl)-2,2-dimethylcyclopropanecarboxylate,2-methyl-3-propargyl-4-oxo-2-cyclopenten-1-yl3-(2-methyl-1-propenyl)-2,2-dimethylcyclopropanecarboxylate,2,3,5,6-tetrafluorobenzyl3-(2,2-dichloroethenyl)-2,2-dimethylcyclopropanecarboxylate (m.p.: 32°C.), chlorpyrifos-methyl (m.p.: 40-50° C.), and4-hydroxy-6-methyl-3-(4-methylpentanoyl)-2-pyrone (m.p.: 40-50° C.).

Examples of synergists (auxiliary agents) for enhancing performance ofthe mothproofing agents and insecticides includeN-(2-ethylhexyl)-bicyclo[2.2.1]-hepta-5-ene-2,3-dicarboxyimide andpiperonyl butoxide.

Examples of repellents include N,N-diethyl-m-toluamide, ethyl3-(N-butyl-N-acetyl)-aminopropionate, sec-butyl2-(2-hyrdoxy-ethyl)-piperidine-1-carboxylate, 2-hydroxyethyl-n-octylsulfide, carane-3,4-diol (m.p.: about 30° C.), and p-menthane-3,8-diol(m.p.: 65-70° C.).

Examples of plant-originating essential oils include lavender oil,hinoki oil, clove oil, lemongrass oil, lemon oil, lime oil, orange oil,ylang ylang oil, oregano oil, cinnamon oil, thyme oil, sage oil,rosemary oil, peppermint oil, chamomile oil, caraway oil, coriander oil,pine oil, geranium oil, eucalyptus oil, hyssop oil, and patchouli oil.

Examples of antibacterial, antifungal agents include hiba acidic oil,allyl isocyanate, phenethyl isocyanate, thymol, carvacrol,3-methyl-4-isopropylphenol, and hinokitiol (m.p.: 50-60° C.).

Examples of volatile liquids which exhibit no chemical effect and may beemployed include water, alcohols such as ethanol, and isoamyl acetatefor short term display; glycerin, glycols such as propylene glycol andtriethylene glycol, and fragrances such as linalool and geraniol formoderately long term display; and lauryl alcohol, dimethyl phthalate,benzyl benzoate, isopropyl myristate, silicone oil, and liquid mixturesthereof for long term display (extending over one month or longer).

To the aforementioned liquids, other components such as a volatilityregulator may be added in such an amount that does not affect theindicative functions of the liquids. The volatility regulator; e.g.,liquid paraffin, jojoba oil, silicone oil, castor oil, pine oil, or mintoil, can be incorporated in an amount of 20 mass % or less.

Any of these liquids can be incorporated into the aforementionedindicative substrate through a known method; e.g., immersion, injection,or impregnation by dropwise addition.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic plan view showing an example indicative substrateof the period indicator of the present invention;

FIG. 2 is a schematic front view of the indicative substrate of theperiod indicator shown in FIG. 1;

FIG. 3 is a schematic plan view showing a state where only one region ofthe indicative section develops an indication as a result ofvolatilization of the liquid contained in the indicative substrate ofthe period indicator shown in FIGS. 1 and 2;

FIG. 4 is a schematic plan view showing a state where two regions of theindicative section develop an indication after volatilization of theliquid proceeds from the state shown in FIG. 3;

FIG. 5 is a schematic plan view showing a state where all three regionsof the indicative section develop an indication after volatilization ofthe liquid further proceeds from the state shown in FIG. 4;

FIG. 6 is a schematic front view showing another example indicativesubstrate of the period indicator of the present invention;

FIG. 7 is a schematic plan view showing a state where only one region ofthe indicative section develops an indication as a result ofvolatilization of the liquid contained in the indicative substrate ofthe period indicator shown in FIG. 6;

FIG. 8 is a schematic plan view showing a state where two regions of theindicative section develop an indication after volatilization of theliquid proceeds from the state shown in FIG. 7;

FIG. 9 is a schematic plan view showing a state where all three regionsof the indicative section develop an indication after volatilization ofthe liquid further proceeds from the state shown in FIG. 8;

FIG. 10 is a schematic front view showing yet another example indicativesubstrate of the period indicator of the present invention;

FIG. 11 is a schematic plan view showing a state where only one regionof the indicative section develops an indication as a result ofvolatilization of the liquid contained in the indicative substrate ofthe period indicator shown in FIG. 10;

FIG. 12 is a schematic plan view showing a state where two regions ofthe indicative section develop an indication after volatilization of theliquid proceeds from the state shown in FIG. 11;

FIG. 13 is a schematic plan view showing a state where all three regionsof the indicative section develop an indication after volatilization ofthe liquid further proceeds from the state shown in FIG. 12;

FIG. 14 is a schematic front view showing still another exampleindicative substrate of the period indicator of the present invention;

FIG. 15 is a schematic plan view showing a state where two regions ofthe indicative section develop an indication as a result ofvolatilization of the liquid contained in the indicative substrate ofthe period indicator shown in FIG. 14;

FIG. 16 is a schematic plan view showing a state where four regions ofthe indicative section develop an indication after volatilization of theliquid proceeds from the state shown in FIG. 15; and

FIG. 17 is a schematic plan view showing a state where all regions ofthe indicative section develop an indication after volatilization of theliquid further proceeds from the state shown in FIG. 16.

BEST MODE FOR CARRYING OUT THE INVENTION

Referring to FIGS. 1 and 2, portions of one surface of a substrate 4which had been colored blue were coated with anindicative-section-forming material containing a binder and finelydivided particle matter of a white inorganic pigment which has a lowlight refractive index. The indicative-section-forming material allows aliquid chemical to permeate through the material. Thereby, an indicativesubstrate “a” of a period indicator was formed, wherein a whiteindicative section consisting of three isosceles triangular regions 1,2, and 3 was disposed on the surface of one side of the substrate “a”.The surface of the other side of the substrate which bears no indicativesection was covered by a covering 5.

Since the coating amount per unit area was sequentially reduced fromregion 1 to region 2 then to region 3, the height as measured from thesubstrate surface was the largest in region 1, followed by region 2, andthe smallest in region 3. A period indicator A was produced byimpregnating the indicative substrate “a” with an oily liquid (notshown).

The indication mechanism of the period indicator of the presentinvention will next be described with reference to FIGS. 3 to 5 whichillustrate the course of development of an indication in respectiveregions of the indicative section until the contained liquid has beencompletely lost through volatilization. The development of color isdescribed as follows (orderly arranged starting from intense blue):dark→blue→blue→light blue→pale blue→pale whitey blue→white.

Although not shown, in the initial stage, when the indicative substrate“a” is sufficiently filled with a liquid, substrate 4 becomes to assumean intense color, specifically, dark blue. Since all the regions 1, 2,and 3 of the indicative section become transparent because of their lowlight refractive index, they hand over the color of the substratesurface and thus remain unnoticeable. In this stage, volatilization ofthe liquid begins. Although the liquid is allowed to volatilize fromevery surface of the period indicator, any change is yet to be observedon the surfaces of the indicator. This represents a situation where theliquid is sufficiently transferred from the substrate to the indicativesection.

FIG. 3 shows a situation where volatilization of the liquid hasproceeded to some degree, and as a result, region 1 has becomerecognizable as a small triangle which assumes a color of light bluewith a weak contrast against the color developed by the substratesurface.

FIG. 4 shows a situation where volatilization of the liquid hasproceeded further, and as a result, region 1 which assumes a color ofpale blue with a moderately increasing contrast against the colordeveloped by the substrate surface, is recognizable, and simultaneously,region 2 has become recognizable as a small triangle which assumes acolor of light blue with a weak contrast against the color developed bythe substrate surface.

FIG. 5 shows a situation where volatilization of the liquid hasproceeded even further, and as a result, regions 1 and 2 are displayedclearly with enhanced whiteness, and region 3, which assumes a color ofpale whitey blue with a strong contrast against the color developed bythe substrate surface, has become clearly noticeable.

When volatilization further proceeds and almost the entirety of thecontained liquid has been lost, regions 1, 2, and 3 all increase thelevel of whiteness, showing the whiteness similar to that presented bythe indicative section of the indicative substrate “a” before it wasimpregnated with the liquid.

FIG. 6 is a front view showing another indicative substrate of a periodindicator, and FIGS. 7 through 9 show the course of development ofindication in respective regions of the indicative section during theperiod until the liquid in the period indicator has been completelyvolatilized.

Portions of one surface of a substrate 14 which had been colored bluewere coated with an indicative-section-forming material containing abinder and finely divided particle matter of a white inorganic pigmentwhich has a low light refractive index. The indicative-section-formingmaterial allows a liquid chemical to permeate through the material.Thereby, an indicative substrate “b” of a period indicator was formed,wherein on the surface of the substrate “b” was disposed a whiteindicative section including three regions 11, 12, and 13 which werediscretely disposed with spaces between the regions, the regionsrepresenting three segments or parts composing an isosceles triangle.

The area proportions of the regions 11, 12, and 13 are 4.7:2.9:1. Sinceregions 11, 12, and 13 are configured to bear coating in progressivelysmaller amounts per unit area in this sequence, region 11 is thetallest, region 12 is second to region 11, and region 13 is the shortestin height as measured from the substrate surface. A period indicator Bwas produced by impregnating the indicative substrate “b” with an oilyliquid (not shown).

FIG. 7 shows a situation where, as volatilization of liquid hasprogressed to some extent, region 11, having a large area and bearing agreat amount of coating, has become recognizable as a trapezoid whichassumes a color of light blue with a low contrast against the colordeveloped by the substrate surface.

FIG. 8 shows a situation where volatilization of liquid has furtherprogressed, and as a result, region 11 has now become recognizable ashaving enhanced whiteness and moderately high contract against the colordeveloped by the substrate surface, and region 12 has becomerecognizable as a light blue trapezoid having a low contrast against thecolor developed by the substrate surface.

FIG. 9 shows a situation where volatilization of liquid has even furtherprogressed, and as a result, regions 11 and 12, assuming a virtuallywhite color, are displayed clearly, and region 13 is recognizable as alight blue trapezoid.

When volatilization further proceeds and almost the entirety of thecontained liquid has been lost, regions 11, 12, and 13 all increase thelevel of whiteness, showing the whiteness similar to that presented bythe indicative section of the indicative substrate “b” before it wasimpregnated with the liquid.

FIG. 10 is a front view showing yet another indicative substrate of aperiod indicator, and FIGS. 11 through 13 show the course of developmentof indication in respective regions of the indicative section during theperiod until the liquid in the period indicator has been completelyvolatilized.

Portions of one surface of a substrate 24 which had been colored bluewere coated with an indicative-section-forming material containing abinder and finely divided particle matter of a white inorganic pigmentwhich has a low light refractive index. The indicative-section-formingmaterial allows a liquid chemical to permeate through the material.Thereby, an indicative substrate “c” of a period indicator was formed.This substrate “c” was configured such that, on the surface of thesubstrate “c” was disposed a white indicative section including threeregions 21, 22, and 23 arranged to flank one on another with no spacebetween the regions, the regions representing three segments or partscomposing an isosceles triangle.

The area proportions of the regions 21, 22, and 23 are 4.7:2.9:1. Sinceregions 21, 22, and 23 are configured to bear coating in progressivelysmaller amounts per unit area in this sequence, region 21 is thetallest, region 22 is second to region 21, and region 23 is the shortestin height as measured from the substrate surface. A period indicator Cwas produced by impregnating the indicative substrate “c” with an oilyliquid (not shown).

FIG. 11 shows a situation where, as volatilization of liquid hasprogressed to some extent, region 21, having a large area and bearing agreat amount of coating, has become recognizable as a trapezoid whichassumes a color of light blue with a low contrast against the colordeveloped by the substrate surface.

FIG. 12 shows a situation where volatilization of liquid has furtherprogressed, and as a result, region 21 has now become recognizable ashaving enhanced whiteness and moderately high contract against the colordeveloped by the substrate surface, and region 22 has becomerecognizable as a light blue trapezoid having a low contrast against thecolor developed by the substrate surface.

FIG. 13 shows a situation where volatilization of liquid has evenfurther progressed, and as a result, regions 21 and 22, assuming avirtually white color, are displayed clearly, and region 23 isrecognizable as a light blue trapezoid.

When volatilization further proceeds and almost the entirety of thecontained liquid has been lost, regions 21, 22, and 23 all increase thelevel of whiteness, showing the whiteness similar to that presented bythe indicative section of the indicative substrate “c” before it wasimpregnated with the liquid.

FIG. 14 is a front view showing still another indicative substrate of aperiod indicator, and FIGS. 15 through 17 show the course of developmentof indication in respective regions of the indicative section during theperiod until the liquid in the period indicator has been completelyvolatilized.

Portions of one surface of a substrate 34 which had been colored bluewere coated with an indicative-section-forming material containing abinder and finely divided particle matter of a white inorganic pigmentwhich has a low light refractive index. The indicative-section-formingmaterial allows a liquid chemical to permeate through the material.Thereby, an indicative substrate “d” of a period indicator was formed.This substrate “d” was configured such that, on the surface of thesubstrate “d” was disposed a white indicative section including threeregions 31, 32, and 33. Regions 31, 32 and 33 represent a largetriangle, a small triangle, and letters “END,” respectively. Sinceregions 31, 32, and 33 are configured to bear coating in progressivelysmaller amounts per unit area in this sequence, region 31 is thetallest, region 32 is second to region 31, and region 33 is the shortestin height as measured from the substrate surface. A period indicator Dwas produced by impregnating the indicative substrate “d” with an oilyliquid (not shown).

FIG. 15 shows a situation where, as volatilization of liquid hasprogressed to some extent, region 31, having a large area and bearing agreat amount of coating, has become recognizable as a triangle whichassumes a color of light blue with a low contrast against the colordeveloped by the substrate surface.

FIG. 16 shows a situation where volatilization of liquid has furtherprogressed, and as a result, region 31 has now become recognizable ashaving enhanced whiteness and moderately high contract against the colordeveloped by the substrate surface, and region 32 has becomerecognizable as a light blue triangle having a low contrast against thecolor developed by the substrate surface.

FIG. 17 shows a situation where volatilization of liquid has evenfurther progressed, and as a result, regions 31 (large triangles) andregions 32 (small triangles) assume a virtually white color and aredisplayed clearly, and region 33 is recognizable as letters “END” inlight blue.

When volatilization further proceeds and almost the entirety of thecontained liquid has been lost, regions 31, 32, and 33 all increase thelevel of whiteness, showing the whiteness similar to that presented bythe indicative section of the indicative substrate “d” before it wasimpregnated with the liquid.

In the period indicator of the present invention, in each step instepwise indication, the indicative section starts to develop color whenvacant pores are produced in the vicinity of the surface of theindicative section. Under such a situation, however, the lower part ofthe indicative section remains to be filled with a liquid, andtherefore, masking performance for the indicative section is low.Therefore, the indicative section assumes a diluted color of that of thesubstrate surface. For example, when the substrate is blue, the bluecolor is diluted to assume pale blue. As volatilization of the liquidproceeds, generation of vacant pores extends to the lower part of theindicative section. In this situation also, so long as the substratecontains the liquid, supply of the liquid to the indicative section willnever stop, and therefore, the number of vacant pores in the indicativesection gradually increases until volatilization is complete, resultingin a gradual advancement in development of indication (i.e., becomingwhitey). The greater the amount of coating applied to the indicativesection, the greater the total vacant pore volume in the indicativesection, calling for an increased amount of the liquid to fill thevacant pores in the indicative section. Therefore, when the liquidcontent of the substrate is reduced due to volatilization of the liquid,shortage of liquid supply occurs earlier, permitting earlier start ofindication.

Accordingly, the present invention provides a period indicator which caneffectively invite the user's attention, since a variety of signs—whichdiffer in the moment of developing indication—are available by simplytuning the amount of coating or the area of coating of the indicativesection, either individually or in combination.

The present invention will next be described by way of examples, whichshould not be construed as limiting the invention thereto. Evaluation ofthe period indicator of the present invention regarding the developmentof a sign in the indicative section thereof was performed as follows.[Evaluation of indication development in the indicative section] Eachperiod indicator was left to stand under predetermined conditions,whereby liquid contained therein was allowed to volatilize. Developmentof a sign in the indicative section was visually observed and evaluatedon the basis of the following criteria.

-   -   DD: Sign can't be recognized.    -   CC: Blurred sign substantially prevents recognition of the sign.    -   BB: Difference in color at border portions is observed, whereby        sign can be recognized.    -   AA: Great difference in color at border portions is observed,        whereby sign can be clearly recognized.

EXAMPLE 1

An indicative substrate “a” as shown in FIGS. 1 and 2 was prepared inthe following manner.

A polypropylene film (covering 5) was overlaid on the surface of oneside of a blue wet-laid nonwoven fabric, thereby forming a substrate 4.On the substrate 4, an indicative section containing three aligned,isosceles triangular regions 1, 2, and 3 was formed through screenprinting by use of a material containing amorphous silica. The amountsof coating per unit surface area of the regions 1, 2, and 3 of theindicative section were adjusted to three different levels: 120 g/m², 55g/m², and 35 g/m², respectively. The regions of the indicative sectiondiffer in whiteness from one another due to a difference in maskingperformance caused by different amounts of coating. To the thus-formedindicative substrate “a,” oily liquid was incorporated, whereby a periodindicator A was prepared.

The above materials and methods are described in more detail below.

-   Substrate: Blue wet-laid nonwoven fabric (150 g/m², 20 mm×54 mm×400    μm)-   Covering: Polypropylene film (20 mm×54 mm×100 μm)-   Indicative-section-forming material: Prepared by mixing amorphous    silica and an acrylic binder (solid content ratio: 1/0.5) with    additives (i.e., a dispersant (sodium hexametaphosphate) and a    viscosity modifier (carboxymethyl cellulose))-   Liquid contained: Dimethyl phthalate (80 mg) incorporated through    injection.

The above period indicator A was left to stand at room temperature (23°C.) under calm conditions, whereby liquid contained therein wasvolatilized. During the course of volatilization, development of a signin the indicative section was visually observed. The results are shownbelow. Regions 1 2 3 Amount of liquid contained 100% DD DD DD  73 CC DDDD  28 BB CC DD  15 AA BB CC  8 AA AA BB  1 AA AA AA

EXAMPLE 2

An indicative substrate “b” as shown in FIG. 6 was prepared in thefollowing manner.

Through use of a material similar to that employed in Example 1, anindicative section consisting of regions 11, 12, and 13 was formed onthe substrate surface through screen printing. The three regions formingin combination an isosceles triangle were discretely disposed withspaces between the regions. The coating amounts of theindicative-section-forming material applied to the regions weredifferent from one another. The area proportions of the regions 11, 12,and 13 of the indicative section were 4.7:2.9:1. The amounts of coatingper unit surface area of the regions 11, 12, and 13 were 82 g/m², 60g/m², and 24 g/m², respectively. Similar to the case of Example 1,dimethyl phthalate was incorporated into the thus-formed indicativesubstrate “b”, whereby a period indicator B was prepared.

The above period indicator B was left to stand at room temperature (23°C.) under calm conditions, whereby liquid contained therein wasvolatilized. During the course of volatilization, development of a signin the indicative section was visually observed. The results are shownbelow. Regions 11 12 13 Amount of liquid contained 100% DD DD DD  54 CCDD DD  32 BB CC DD  19 BB CC DD  8 AA BB CC  1.5 AA AA BB

EXAMPLE 3

An indicative substrate “c” as shown in FIG. 10 was prepared in thefollowing manner.

Through use of a material similar to that employed in Example 1, anindicative section consisting of regions 21, 22, and 23 was formed onthe substrate surface through screen printing. The three regions formingin combination an isosceles triangle were disposed in contact with oneanother. The coating amounts of indicative-section-forming materialapplied to the regions were different from one another. The areaproportions of the regions 21, 22, and 23 of the indicative section were4.7:2.9:1. The amounts of coating per unit surface area of the regions21, 22, and 23 were 68 g/m², 35 g/m², and 18 g/m², respectively. Similarto the case of Example 1, dimethyl phthalate was incorporated into thethus-formed indicative substrate “c”, whereby a period indicator C wasprepared.

In order to accelerate changes in development of a sign, the aboveperiod indicator C was left to stand under thermostatic conditions (50°C.), whereby liquid contained therein was volatilized. Development of asign in the indicative section was visually observed. The results areshown below. Regions 21 22 23 Amount of liquid contained 100% DD DD DD 45 CC DD DD  32 BB CC DD  19 BB BB CC  8 AA BB BB  1 AA AA AA

EXAMPLE 4

An indicative substrate having the same form as an indicative substrate“d” of FIG. 14 except for being colored orange was prepared in thefollowing manner.

A pigment of orange color was applied to a surface of a filter paper(basis weight: 150 g/m², 30 mm×40 mm×thickness 500 μm) through gravureprinting, to thereby prepare a substrate having a surface having a colorof L*=73 in the L*a*b* calorimetric system as specified by JIS 8730. Nocovering was overlaid on the non-colored surface of the substrate. Onthe colored surface of the substrate, an indicative section containingthree regions 31, 32, and 33 was formed through screen printing by useof an indicative-section-forming material similar to that employed inExample 1, the material containing amorphous silica. The region 31 hastwo isosceles triangular parts which face each other and are separatelydisposed in the vicinity of opposite ends of the substrate. The region32 has two smaller isosceles triangular parts which also face each otherand are disposed inside the isosceles triangular portions of the region31. The region 33 is disposed in a center portion on the substratesurface and takes the form of small letters “END.” The amounts ofcoating per unit surface area of the regions 31, 32, and 33 of theindicative section were 32 g/m², 26 g/m², and 14 g/m², respectively.

Into the thus-formed substrate, a mothproofing agent (40 mg) (i.e.,1-ethynyl-2-methyl-2-pentenyl3-(2-methyl-1-propenyl)-2,2-dimethylcyclopropanecarboxylate) wasincorporated through injection, thereby preparing a period indicator.

In order to accelerate changes in development of a sign, the aboveperiod indicator was left to stand under thermostatic conditions (40°C.), whereby the mothproofing liquid chemical was volatilized.Development of a sign in the indicative section was visually observed.The results are shown below. Regions 31 32 33 Amount of liquid contained100% DD DD DD  62 DD DD DD  33 CC DD DD  26 CC CC DD  20 BB CC DD  17 BBBB DD  8 BB BB CC  5 AA AA BB  0 AA AA AA

The period indicator effectively accomplished three-step indicationstarting from outer portions toward a center portion of the indicator.

Industrial Applicability

The present invention provides a period indicator which displays thequantity-related status of a liquid chemical in a stepwise manner. Theperiod indicator is produced through a simple process by use of anindicative-section-forming material composed of a single componentmaterial. The thus-produced period indicator is useful for indicatingthe period of efficacy of a liquid chemical such as a mothproofingagent, an insecticide, a deodorant, or a fragrance. In addition, theindicator can be configured to have its indicative section consisting ofa plurality of regions, so that the respective regions sequentiallydevelop signs starting from the region of the earliest indication, andthat when the region of the slowest indication has developed itsindication, the entire indicative section conveys a certain message.Therefore, the indicator of the invention can effectively invite theuser's attention.

1. A period indicator comprising a liquid-permeable substrate and anindicative section which is overlaid on a portion of the substrate andwhich is formed from a liquid-permeable material having a low lightrefractive index, the indicator containing a volatile liquid, whereinthe indicative section is formed by coating a surface of the substratewith an indicative-section-forming material prepared by mixing a binderand finely divided particulate matter having a low light refractiveindex, the indicative section comprises two or more regions, and theregions differ in height from one another as measured from the surfaceof the substrate, as_coating amounts per unit area of the indicativesection forming material in the two or more regions differ from oneanother.
 2. The period indicator as recited in claim 1, wherein the twoor more regions that form the indicative section are discretely disposedon the substrate.
 3. The period indicator as recited in claim 1, whereineach of the coating amounts per unit area of the indicative sectionforming material in the two or more regions that form the indicativesection is within the range of 4 to 150 g/m², with the coating amount ina region where the coating amount is the smallest being 4 to 40 g/m² anddifference in the coating amounts between the two or more regions beingnot less than 5 g/m².